The earth has survived asteroid strikes and comet collisions, continental drift, orbital perturbations, massive Deccan Plateau-type lava flows, colossal volcanic eruptions, and heaven knows what other types of catastrophes over the last few billion years and life has not only survived, it has continued to flourish and evolve. The atmosphere-ocean system is filled with all sorts of moderating feedback mechanisms which keep it fairly well under control, except for an occasional ice age now and then, and even these events appear to be localized. I can't imagine us doing anything with our industrial activities which would precipitate a runaway event leading to a Venus- or Mars-like scenario and an uninhabitable planet.

But the same fossil evidence which assures us that world climate oscillates within acceptable limits also testifies to the fact that oscillations do happen; and although they may not turn the world into an uninhabitable wasteland, they may very well affect natural systems we have become highly dependent on. Even a small change in climate could greatly disrupt modern mechanized agriculture or settlement patterns which have been centuries in the making. It is not the end of the world or of life, or even mankind we have to worry about. But civilization may very will threatened.

Imagine the abandonment of agriculture in the American plains, or Europe's climate suddenly becoming like northern Canada's. Desertification and sea-level rise may not kill anyone outright, but it might make vast productive tracts of the planet inhospitable. Even if the Sahara or the Amazon basin become the new wheat and corn belts of the planet as a compensation, the political and social problems which will result are incalculable.

The climate chaos and doomsayers do us a disservice because they discredit responsible warnings about climate change and play right into the hands of those who would like us to believe that there is nothing to worry about and that we shouldn't or can't do anything about it.